Panic from renderer.DrawPoint about go-sdl2

[aqiank]

Can you tell me what OS you are running this on and which version of Go you are using? It doesn't seem to crash on mine.

[EvanTheB]

go version go1.3 linux/amd64
I am on debian jessie/sid

[aqiank]

Hm..it still doesn't panic. What happens if you put, say, sdl.Delay(16) inside frame update? Does the issue still appear?

[EvanTheB]

Yes I still get the issue. updated to
go version go1.3.1 linux/amd64
fatal error: unexpected signal during runtime execution
[signal 0xb code=0x1 addr=0x0 pc=0x7fe7753971c9]

runtime stack:
runtime: unexpected return pc for runtime.sigpanic called from 0x7fe7753971c9
runtime.throw(0x7df645)
/usr/lib/go/src/pkg/runtime/panic.c:520 +0x69
runtime: unexpected return pc for runtime.sigpanic called from 0x7fe7753971c9
runtime.sigpanic()
/usr/lib/go/src/pkg/runtime/os_linux.c:222 +0x3d

I cant really decipher these lines. I think signal is a SEGV seg fault, unexpected return pc? Is the crash being thrown by a system call or something? Maybe should kick this up to a go bug...

[EvanTheB]

OK so I had some assistance from the #go-nuts forum:
james4k: you will need to call runtime.LockOSThread() on whatever goroutine you are doing your GL calls on
james4k: and do all of your GL calls in that goroutine
james4k: GL maintains its state per-thread, while Go's runtime will execute its goroutines on a number of OS threads

The problem seems fixed, this "runtime.LockOSThread()" requirement probably needs to go somewhere prominent, at least until the doc is happening. Maybe in the readme?

[aqiank]

Thanks for finding the solution, Evan. Could you create two minimal examples (one that crashes and one that doesn't) and describe how you fixed the problem? I'll add the solution to the readme.

[EvanTheB]

Sorry about the silence, I moved cities and got a new job! I have not been able to replicate the issue on my new computer.